Improving the hydrogen cycling properties by Mg addition in Ti-V-Zr-Nb refractory high entropy alloy

• A novel high entropy alloy containing Mg and refractory elements has been prepared by mechanochemical synthetic method under inert atmosphere. The Mg0.10Ti0.30V0.25Zr0.10Nb0.25 alloy adopts a single-phase bcc lattice and can absorb hydrogen within 1 minute at room temperature forming a hydride phase with 1.7 H/M (2.7 wt.%) capacity. During the reaction with hydrogen the alloy undergoes a single-step and reversible phase transformation from bcc (alloy) to fcc lattice (hydride). The absorption/desorption cycling properties prove a small fading of the capacity for the first cycle followed by stabilization to 1.5 H/M (2.4 wt.%) for the next cycles. A simple comparison between this quinary HEA and the quaternary alloy containing only refractory elements Ti0.325V0.275Zr0.125Nb0.275 proves an important enhancement of the cycling properties by Mg addition. These insights seem to suggest that insertion of light-weighted metals such as, Mg, can guide future design of novel HEA with improved performances for hydrogen storage.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Materialteknik -- Metallurgi och metalliska material (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering -- Metallurgy and Metallic Materials (hsv//eng)

NATURVETENSKAP  -- Kemi -- Materialkemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Materials Chemistry (hsv//eng)

Nyckelord

High entropy alloys

Hydrogen absorption/desorption cycling

Synchrotron-XRD

In situ neutron diffraction

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